Various methods by which electric energy consumption can be decreased during peak hours have been proposed, for example:
(1) The bi-energy systems used by the Province of Quebec, in Canada, exemplify this by enabling a transition from electric heating to some other form of heating such as oil or gas, to occur during periods of low temperature. The capability of increased export, outside of Quebec, during periods of intense cold, further demonstrates the desirability of such bi-energy systems. PA1 (2) Canadian patent No. 1.090.307 (CANN and AL), issued Nov. 25, 1980, proposes a transition from a furnace heating system to a heat pump controlled system. PA1 (3) Canadian patent No. 1.187.462 (IVERSEN et. AL.), issued May 21, 1985, proposes a system based upon the combination of hot water heating and a heat pump. PA1 (i) means for detecting a predetermined pulse duration modulation signal embedded in the level of the supply voltage provided by the distribution network; and PA1 (ii) means for transmitting electric power originating from the distribution network to the load, the aforesaid means for transmitting comprising means for reducing the level of average power transmitted to the load, in response to a detection of said pulse duration modulation signal in the level of supply voltage. PA1 (i) means for detecting modulation signal in the level of supply voltage supplied by said electric energy distribution network; and PA1 (ii) means for transmitting electric power originating from the distribution network to said loads of the aforesaid group, the aforesaid means for transmitting comprise means for reducing the level of average power transmitted to the group of loads in response to a detection of said pulse duration modulation signal in the level of supply voltage. PA1 (i) means for modulating a predetermined pulse duration modulation signal in the level of supply voltage provided by the distribution network; and PA1 (ii) a controller associated with the aforesaid load, comprising: PA1 (i) modulation of a predetermined pulse duration modulation signal in the level of supply voltage provided by the distribution network to the dissipative loads, said duration modulation signal corresponding to at least one of said loads ; PA1 (ii) detection of the aforesaid pulse duration modulation signal in the level of supply voltage at the level of each of said dissipative loads; and PA1 (iii) reduction of electric power provided by the distribution network to said at least one load which corresponds to said pulse duration modulation signal. PA1 means for detecting a predetermined pulse duration modulation signal in the level of supply voltage provided to said residence, and generating a signal accordingly; and PA1 means connected to said electricity meter for modifying said scale of charges when said signal is generated.
However, there is a drawback with the bi-energy systems that are presently in operation, the transition from one type of energy to another is a function of the temperature. Furthermore, these bi-energy systems cannot be controlled at distance, by the electricity production companies, to reduce consumption when it is required to do so.
Another method that is known to effectively reduce the level of average power supplied by a distribution network involves a continuous lowering of the level of voltage during a generally lengthy interval of time (during peak hours, for example). However, this solution presents an inconvenience, other electric and electronic control devices supplied by the distribution network, such as motors, are disrupted.
Methods by which the applications of electric power to dissipative loads using high frequency modulated pulses superimposed to the voltage line at the consumer level have also been proposed.
Such methods are described in the Canadian patents No. 1.128.162 (BELCHER and AL), issued Jul. 20, 1982, and No. 1.118.512 (CLEARY and AL), issued Feb. 16, 1982. On a larger scale. however, such brief pulses may not be transmitted through the electric energy distribution network because they are filtered, i.e. they are blocked by the transformers.
Consequently, on electric power production and distribution network, a company will be unable to manage electricity consumption by its own distribution network by means of such transmitted pulses.
Load management methods through digitally encoded step voltage signals have been proposed in U.S. Pat. No. 4,686,630 (MARSLAND et. al.). Such a binary transmission involves many transitions which wear the electrical contact of the tap transformers used to that effect. The more sophisticated the transmission, the more the wear and the more are the chances of error in the transmission, which implies a reduced reliability of the transmission. Multilevel values of the average level of the power line voltage could also be used in order to diminish the number of bits needed for a given transmission. However, such a method would affect the lighting level in households and also wear faster the tap transformers.